This is a note to let you know that I've just added the patch titled
riscv: Fix text patching when IPI are used
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
riscv-fix-text-patching-when-ipi-are-used.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 941481db4a1d865e2a28886ec9ef36d52a878989
Author: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Date: Thu Feb 29 13:10:56 2024 +0100
riscv: Fix text patching when IPI are used
[ Upstream commit c97bf629963e52b205ed5fbaf151e5bd342f9c63 ]
For now, we use stop_machine() to patch the text and when we use IPIs for
remote icache flushes (which is emitted in patch_text_nosync()), the system
hangs.
So instead, make sure every CPU executes the stop_machine() patching
function and emit a local icache flush there.
Co-developed-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Reviewed-by: Andrea Parri <parri.andrea@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240229121056.203419-3-alexghiti@xxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Stable-dep-of: 13134cc94914 ("riscv: kprobes: Fix incorrect address calculation")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h
index e88b52d39eac..9f5d6e14c405 100644
--- a/arch/riscv/include/asm/patch.h
+++ b/arch/riscv/include/asm/patch.h
@@ -6,6 +6,7 @@
#ifndef _ASM_RISCV_PATCH_H
#define _ASM_RISCV_PATCH_H
+int patch_insn_write(void *addr, const void *insn, size_t len);
int patch_text_nosync(void *addr, const void *insns, size_t len);
int patch_text_set_nosync(void *addr, u8 c, size_t len);
int patch_text(void *addr, u32 *insns, int ninsns);
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 03a6434a8cdd..6ede2bcce238 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -8,6 +8,7 @@
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/memory.h>
+#include <linux/stop_machine.h>
#include <asm/cacheflush.h>
#include <asm/patch.h>
@@ -75,8 +76,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
make_call_t0(hook_pos, target, call);
/* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
- if (patch_text_nosync
- ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
+ if (patch_insn_write((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
@@ -88,7 +88,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
make_call_t0(rec->ip, addr, call);
- if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE))
+ if (patch_insn_write((void *)rec->ip, call, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
@@ -99,7 +99,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
{
unsigned int nops[2] = {NOP4, NOP4};
- if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
+ if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
@@ -134,6 +134,42 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
return ret;
}
+
+struct ftrace_modify_param {
+ int command;
+ atomic_t cpu_count;
+};
+
+static int __ftrace_modify_code(void *data)
+{
+ struct ftrace_modify_param *param = data;
+
+ if (atomic_inc_return(¶m->cpu_count) == num_online_cpus()) {
+ ftrace_modify_all_code(param->command);
+ /*
+ * Make sure the patching store is effective *before* we
+ * increment the counter which releases all waiting CPUs
+ * by using the release variant of atomic increment. The
+ * release pairs with the call to local_flush_icache_all()
+ * on the waiting CPU.
+ */
+ atomic_inc_return_release(¶m->cpu_count);
+ } else {
+ while (atomic_read(¶m->cpu_count) <= num_online_cpus())
+ cpu_relax();
+ }
+
+ local_flush_icache_all();
+
+ return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+ struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
+
+ stop_machine(__ftrace_modify_code, ¶m, cpu_online_mask);
+}
#endif
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 30e12b310cab..78387d843aa5 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -196,7 +196,7 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len)
}
NOKPROBE_SYMBOL(patch_text_set_nosync);
-static int patch_insn_write(void *addr, const void *insn, size_t len)
+int patch_insn_write(void *addr, const void *insn, size_t len)
{
size_t patched = 0;
size_t size;
@@ -240,16 +240,24 @@ static int patch_text_cb(void *data)
if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
for (i = 0; ret == 0 && i < patch->ninsns; i++) {
len = GET_INSN_LENGTH(patch->insns[i]);
- ret = patch_text_nosync(patch->addr + i * len,
- &patch->insns[i], len);
+ ret = patch_insn_write(patch->addr + i * len, &patch->insns[i], len);
}
- atomic_inc(&patch->cpu_count);
+ /*
+ * Make sure the patching store is effective *before* we
+ * increment the counter which releases all waiting CPUs
+ * by using the release variant of atomic increment. The
+ * release pairs with the call to local_flush_icache_all()
+ * on the waiting CPU.
+ */
+ atomic_inc_return_release(&patch->cpu_count);
} else {
while (atomic_read(&patch->cpu_count) <= num_online_cpus())
cpu_relax();
smp_mb();
}
+ local_flush_icache_all();
+
return ret;
}
NOKPROBE_SYMBOL(patch_text_cb);
